class_docstr: A context manager to protect command execution from UNC paths.
  
  In the Win32 API, commands can't be invoked with the cwd being a UNC path.
  This context manager temporarily changes directory to the 'C:' drive on
  entering, and restores the original working directory on exit.
  
  The context manager returns the starting working directory *if* it made a
  change and None otherwise, so that users can apply the necessary adjustment
  to their system calls in the event of a change.
  
  Examples
  --------
  ::
      cmd = 'dir'
      with AvoidUNCPath() as path:
          if path is not None:
              cmd = '"pushd %s &&"%s' % (path, cmd)
          os.system(cmd)
code: def __exit__(self, exc_type, exc_value, traceback):
      if self.is_unc_path:
          os.chdir(self.path)
  
imports: from __future__ import print_function
  import os, sys, threading
  import ctypes, msvcrt
  from .None import py3compat
  from ctypes import POINTER
  from ctypes.wintypes import HANDLE, HLOCAL, LPVOID, WORD, DWORD, BOOL, ULONG, LPCWSTR
label_desc: Use image node_id 2 for calling the AvoidUNCPath obj's underlying member method code with example usage: obj.__exit__(exc_type, exc_value, traceback) without return types